Many cellular functions are mediated by levels of adenosine 3′,5′-cyclic monophosphate (cAMP). Such cellular functions can contribute to inflammatory conditions and diseases including asthma, inflammation, and other conditions (Lowe and Cheng, Drugs of the Future, 17(9), 799-807, 1992). It has been shown that the elevation of cAMP in inflammatory leukocytes inhibits their activation and the subsequent release of inflammatory mediators, including TNFα. Increased levels of cAMP also lead to the relaxation of airway smooth muscle. In addition, excessive or unregulated TNFα production has been implicated in a number of disease conditions including but not limited to autoimmune and inflammatory diseases. Specific disease conditions include endotoxemia and/or toxic shock syndrome [Tracey, et al., Nature 330, 662-664 (1987) and Hinshaw, et al., Circ. Shock 30, 279-292 (1990)], rheumatoid arthritis, inflammatory bowel disease, cachexia [Dezube, et al., Lancet, 335 (8690), 662 (1990)], lupus and cancer.
The primary cellular mechanism for the inactivation of cAMP is the breakdown of cAMP by a family of isoenzymes referred to as cyclic nucleotide phosphodiesterases (PDE) [Beavo and Reitsnyder, Trends in Pharm., 11, 150-155, 1990]. There are greater than ten known members of the family of PDEs. It is well documented that the inhibition of PDE type IV (PDE 4) enzyme is particularly effective in both the inhibition of inflammatory mediator release and the relaxation of airway smooth muscle (Verghese, et al., Journal of Pharmacology and Experimental Therapeutics, 272(3), 1313-1320, 1995].
Increasing cAMP levels (e.g., inhibiting PDE 4) and/or thus decreasing TNFα levels constitutes a valuable therapeutic strategy for the treatment of many inflammatory, infectious, immunological, and malignant diseases. These include but are not restricted to: pulmonary diseases, septic shock, sepsis, endotoxic shock, hemodynamic shock and sepsis syndrome, post ischemic reperfusion injury, malaria, mycobacterial infection, meningitis, many types of psoriasis and other dermal diseases, congestive heart failure, fibrotic disease, cachexia, graft rejection, cancer, tumor growth, undesirable angiogenesis, autoimmune disease, opportunistic infections in AIDS, rheumatoid arthritis, rheumatoid spondylitis, osteoarthritis, other arthritic conditions, inflammatory bowel disease, Crohn's disease, ulcerative colitis, multiple sclerosis, systemic lupus erythematosis, ENL in leprosy, radiation damage, and hyperoxic alveolar injury.
In addition, a variety of other diseases and disorders are also associated with, or characterized by, undesired angiogenesis. For example, enhanced or unregulated angiogenesis has been implicated in a number of diseases and medical conditions including, but not limited to, ocular neovascular diseases, choroidal neovascular diseases, retina neovascular diseases, rubeosis (neovascularization of the angle), viral diseases, genetic diseases, inflammatory diseases, allergic diseases, tumor growth and autoimmune diseases. Examples of such diseases and conditions include, but are not limited to: diabetic retinopathy; retinopathy of prematurity; corneal graft rejection; neovascular glaucoma; retrolental fibroplasia; arthritis; and proliferative vitreoretinopathy.
Accordingly, compounds that can control angiogenesis, inhibit PDE 4, and/or inhibit the production of certain cytokines, including TNFα, may be useful in the treatment and prevention of various diseases and conditions.